ISL1

ISL1, or Islet-1, is a LIM-homeodomain transcription factor encoded by the ISL1 gene in humans. It belongs to the LIM-homeodomain (LIM-HD) protein family, which combines DNA-binding capability with protein–protein interaction domains to regulate gene expression during development and in certain adult cell types. ISL1 functions as a regulatory node in multiple embryonic lineages.

In the nervous system, ISL1 is expressed in motor neuron progenitors of the ventral spinal cord and hindbrain, where it promotes motor and autonomic neuron differentiation. It often operates within transcriptional complexes that include cofactors such as LHX family proteins, helping to specify neuronal identity in response to developmental signals.

ISL1 also marks and contributes to endocrine progenitors in the developing pancreas, contributing to the formation of pancreatic islets and insulin-producing beta cells. Experimental models show that ISL1 participates in endocrine cell development, and disruption can impair the formation and maturation of islet cells.

In cardiac development, ISL1 is expressed in certain cardiac progenitor populations and supports normal heart formation, including structures derived from the outflow tract and conduction system. Loss of Isl1 function in model organisms is associated with defects in heart morphogenesis, highlighting its role in cardiac lineage specification.

Clinically and in research, ISL1 serves as a marker for progenitor and differentiated cell populations in developmental biology and stem cell studies. Its involvement in lineage specification makes it a focus of protocols aiming to derive pancreatic or cardiac cell types from pluripotent stem cells and to model congenital disorders of the heart and pancreas.